1. Field of the Invention
The present invention relates to a rolling guide unit that guides an object to be moved along a curve path, and which is equipped on, for example, a machine tool or industrial robot.
2. Description of the Prior Art
An example of this type of rolling guide unit of the prior art is shown in FIG. 1. Furthermore, although the rolling guide unit is disclosed in Japanese Patent Laid-Open Publication No. 63-186028, a similar constitution is also disclosed in Japanese Patent Laid-Open Publication No. 62-101914.
As shown in FIG. 1, this rolling guide unit is equipped with track rail 1, in which one track each in the form of track groove 1a is formed on both the right and left sides along the lengthwise direction, a slider in the form of slide unit 2 able to move relative to the track rail 1, and a plurality of rolling elements in the form of balls (not shown) arranged and contained within a rolling element circulating path (not shown) formed in the slide unit 2 that bear the load between track rail 1 and slide unit 2 by circulating while rolling over the track grooves 1a.
As shown in the drawing, track rail 1 has a constant curvature in the lengthwise direction, and slide unit 2 moves along this curvature. Furthermore, as is clear from the drawing, the cross-section of track rail 1 is of a roughly rectangular shape, while the cross-section of slide unit 2 is roughly U-shaped, with the slide unit 2 being juxtaposed about the track rail 1.
Although the above-mentioned curved movement type of rolling guide unit was developed for the purpose of accommodating increasingly complex operation modes in apparatuses such as industrial robots and so forth without being limited to simple linear, reciprocating operation, the curved movement type of rolling guide units have recently been required to have increased load capacity and rigidity to be able to withstand larger loads, be able to obtain a smooth operating state by effectively absorbing vibrations and reducing noise levels, as well as achieve a longer service life. However, the above-mentioned rolling guide unit of the prior art is still unable to obtain adequate results with respect to these points.
In addition, in the case of curved movement types of rolling guide units, centrifugal force acts during travel of slide unit 2 corresponding to its speed and curvature. The centrifugal force increases in proportion with the weight (mass) of the object loaded on slide unit 2. Thus, since a large centrifugal force acts on the rolling guide unit in the case of loading a relatively heavy object, it is necessary that the rolling guide unit be able to adequately withstand that centrifugal force.